This invention relates to firearm triggering mechanisms and more particularly to a trigger mechanism for a firearm capable of being activated with substantially reduced trigger force.
A major factor in determining the accuracy of a trigger actuated firearm resides in the user's ability to "squeeze" or release the trigger. A practical trigger in most weapons requires a substantial pressure to fire the weapon. A typical manually operated bolt weapon requires a user to impart about 2 to 3 pounds of force to activate the trigger, while an automatic weapon may require 3 to 5 pounds of force.
It can be easily ascertained that the user in imparting these forces via his trigger finger, will move or vibrate the weapon in doing so and this, of course, will adversely affect the accuracy of his shot.
Due to these and other considerations, there exists in the prior art, a mechanism typically referred to as a "hair trigger". Such a mechanism does not require a large trigger force to fire the weapon. These mechanisms are typically implemented by providing a very shallow recess on the hammer; which recess engages with a mechanism coupled to the trigger. Hence, a slight movement of the trigger removes the mechanism from the notch, allowing the hammer to go forward to strike the firing pin.
In a proper weapon, the hammer is usually cocked at a full position on the positive side of a null, so that when the hammer is released by the trigger, it will move rapidly toward the firing pin. In automatic weapons, the "hair trigger" of the prior art cannot be used. This is so as the shallow hammer notch and polished sear for restraining the hammer to enable hair trigger operation, are much too critical and the weapon may fire during automatic operation without using the trigger. For example, an automatic weapon employing a hair trigger mechanism may be fired during bolt return or chambering of a fresh cartridge.
Thus, the hammer may inadvertently operate due to the force of the bolt and thus ignite a cartridge without trigger pull. This action will cause an automatic or semi-automatic weapon to continuously fire all rounds without trigger pull and it is extremely undesirable, unsafe and unreliable.
Furthermore, the hammer can also be released before the bolt is fully closed to cause a misfire in a "hair trigger" weapon. These inadvertent operations can impose safety hazards on a user and are extremely dangerous and undesirable.
To prevent such problems, many prior art guns employ a hammer which is normally cocked almost at a null position, but slightly on the positive side. These weapons employ a polished sear which engages with a relatively deep hammer notch. The hammer in such weapons is prevented from reaching the null point or going behind or on the negative side of the null, by a mechanical stop which is positioned beneath the hammer on the receiver and located to allow the hammer to engage the sear when cocked. Hence, when the trigger is activated, the sear moves to free itself from the hammer notch, and the hammer once unrestrained, will move forward due to the cocking of the same at the positive side of the null.
Essentially, the hammer in such weapons is cocked so that it is on the positive side of the null and exerts a great force on the sear, which restrains the hammer from moving at this position. In such weapons, the sear is highly polished and fabricated from a hard metal to prevent wear due to the excessive force imposed thereon by the hammer. Such sears wear out relatively fast, break and are subject to great forces and pressures in such weapons.
It is an object of this invention to provide an improved trigger mechanism for a firearm associated with reduced trigger pull and hence, capable of improved accuracy.